None.
The present invention relates to power transmissions in general and, more particularly, to transmissions useful for transmitting rotary power in forward and reverse directions to computer controlled printers, document scanners, automatic document feeders and other office machine applications. Even more particularly, the invention is applicable for use in applying rotary power to accurately position apparatus such as an inkjet printer service station, to operate a scanner drive, and to operation of a paper pick roller in an automatic document feeder capable of separating single sheets of media such as paper, vellum, transparencies, etc. from a stack thereof.
Inkjet printers ordinarily have a printhead servicing station located at some point on the path of travel of a printhead carriage. The servicing station typically includes printhead wipers, a source of printhead servicing fluid and printhead caps, some or all of which may be mounted on a sled or other moveable support to bring the service station into and out of operating proximity to the printheads to be serviced. Automatic document processing apparatus such as scanners and desktop printers typically include a shelf or tray for holding a stack of one or more sheets of documents to be scanned or blank paper or other media to be fed, one sheet at a time, from the stack to the other portions of the document processing apparatus. In such arrangements a driven pick roller having a friction surface may be used to engage the uppermost sheet in a horizontally oriented or downwardly inclined stack to strip the top sheet from the stack and move it parallel to the surface of the stack. The present invention is particularly useful in printhead servicing apparatus and for driving paper pick rollers and in other applications.
It is objective of the present invention to provide a transmission which can selectively couple and de-couple a source rotary drive power to a rotary output shaft only upon application of predetermined angles of rotation of an input shaft or gear in both forward and reverse directions. The design angles of forward and reverse rotation of the input shaft or gear for engaging the transmission need not be the same as the design angles of forward and reverse rotation for disengaging the transmission.
The present invention therefore provides a transmission for transmitting rotary power in forward and reverse directions from a source of rotary power to a load comprising:
a) a rotary input gear for coupling to said source of rotary power;
b) a rotary output gear;
c) a clutch shaft;
d) a clutch gear rotatably mounted on said clutch and drivingly engaged with said input gear;
e) at least one lock plate rotatably mounted on said clutch shaft in frictional engagement with said clutch gear, said lock plate having a socket therein including a radially extending gate and an arcuate slot of first selected angular length accessed by said gate;
f) a shift arm pivotally mounted coaxially with said input gear and frictionally engaged with said input gear, said shift arm including a pawl arcuately moveable into and out of engagement with said lock plate socket; and
g) a shift gear engaged with said input gear, said shift gear being mounted on said shift arm and arcuately moveable with said shift arm between positions of engagement and disengagement with said output gear as said pawl moves into and out of said socket.